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High-Fidelity Multi-Disciplinary Simulation
2014
Dr. Miguel Visbal Principle Research Aerospace Engineer
Aerodynamic Technology Branch Aerospace Vehicles Division (RQV)
Aerospace Systems Directorate
High-Fidelity Multidisciplinary Simulations: Background & Motivations
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High-‐fidelity first-‐principles simulation attributes: üAccurate & truly predictive üProvides fundamental understanding of flow mechanisms üLeverages flow receptivity for enhanced system performance üCost-‐effective approach for “computational experimentation” ü Provides guidance to physics-‐based design-‐oriented approaches
• Spatial & time resolved •Enabled by High-‐Performance Computing •Experimental/ computational synergistic comparisons
ü Challenges persist in the accurate numerical simulation and understanding of dynamic multi-‐physics phenomena relevant to aerospace vehicles, e.g. transition, turbulence, separated flows, non-‐linear aero-‐elasticity, flow control, aero-‐optics, aero-‐acoustics
ü Complex non-‐linear multi-‐disciplinary physics critical to FAD, EE, SUAS ü Failure to account for complex multi-‐disciplinary physics impacts system performance, reliability & life-‐cycle costs
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. 88ABW-2014-3059
Hierarchy of Viscous Flow Simulation
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Direct Numerical Simulation (DNS)
Num
eric
al A
ccur
acy
Large-Eddy Simulation (LES)
Hybrid RANS/LES
Implicit LES (ILES)
ü Unsteady loading ü Aero-elasticity ü Active flow control ü Transition ü Aero-optics ü Acoustics
Reynolds Averaged Navier-Stokes (RANS)
ü Mean flow üsteady loads
Reduced-Order Methods (ROM)
Tim
e-O
n-St
atio
n (h
rs)
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10 Current-Day Technology
Extend Laminarr Flow
Advanced Structures
2015 SensorCraft
Acttiive Aerroelasttic Wing
AAddapapttiivvee StStrrucuctturesures
Flow Conttroll
Structural Anttennas
Computtattiional Methods
Rapid Assessment Fine-scale unsteadiness
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. 88ABW-2014-3059
Computational Framework
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Our Aim
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Discover, Develop, Demonstrate & Transi3on: ü High-‐fidelity solu3ons & approaches ü Fundamental understanding ü Flow control strategies of complex physical phenomena in support of USAF’s
dominant aerospace vehicles
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. 88ABW-2014-3059
Synergistic Collaborative Structure
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In-house team Dr. M. Visbal (Lead) Dr. D. Rizzetta Dr. R. Gordnier Mr. C. Barnes (Co-Op) Dr. D. Garmann (OAI) Dr. M. White (OAI) Dr. P. Morgan (OAI)
AFOSR Dr. D. Smith NRC
Industry GE Research
Academia UM MSU Lehigh Stanford ERAU ….
Summer Faculty
International Bath Univ. (UK) RTO ECL (France)
DoD HPCMO
NASA DARPA
ARO
RQV RQH
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. 88ABW-2014-3059
Product-Driven Research Focus
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Broad speed regime : 0.1 < Mach < 3.0
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. 88ABW-2014-3059
Unsteady Separation & Dynamic Stall
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ü Dynamic stall is induced by large excursions in angle of attack due to surface motion or incoming gusts.
ü Aggressive use of laminar flow over lightweight structures for improved energy efficiency brings about the potential for unforeseen interactions excited by incoming gusts.
ü Coupling of large excursion of transition location, unsteady separation and elastic response may severely impact vehicle dynamics.
ü Generation of abrupt unsteady loading, noise & vibration ü Problem has defied prediction using standard techniques.
ü Outstanding issues: effects of transition & compressibility at realistic Reynolds number
OBJECTIVES üPerform path-‐Uinding high-‐Uidelity LES at increased Re üProvide fundamental understanding of unsteady separation processes üIdentification strategies for effective Ulow control -‐ precursor states for sensing & control with rapid response actuators
ü Discover unforeseen transition-‐motion induced vehicle response with significant implications for energy efUiciency
ü Guide reduced-‐Uidelity approaches ü Transition/ leveraging thru army rotorcraft research
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. 88ABW-2014-3059
Onset of Unsteady Separation & Dynamic Stall Over Pitching Airfoil
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U
α (t)
Ω SD7003 section
Ωo+ = Ω c /U = 0.05
Minf = 0.1 Rec = 0.5 x 106
αo = 4ο
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. 88ABW-2014-3059
Spatio-Temporal Distribution of Surface Pressure
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transition
x
-‐Cp DSV
SLV
-‐Cp
α = 4o
α = 30o
LE suction collapse
DSV
LSB pressure plateau
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. 88ABW-2014-3059
Role of Laminar Separation Bubble
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Low-‐pass Oiltered near-‐wall velocity
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Exploration Dynamic Stall Flow Control
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Control of Dynamic Stall Using HF Pulsed Actuation
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Baseline Forced
Leverage OSU experimental/comp plasma flow control research
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. 88ABW-2014-3059
Streamwise-Oriented Vortex Interactions with Rigid & Flexible Wings
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ü Homogeneous/heterogeneous, close/extended formation flight are envisioned as a potential technology for reduced fuel consumption & improved range; important to operations with limited forward presence.
ü Outstanding issues include: transonic effects at high subsonic speeds, buffeting, coupling of non-‐linear flow phenomena near the wing tip with structural flexibility, severe dynamic load environment with impact on drag reduction beneOits and life-‐cycle fatigue.
ü Study canonical interaction to provide insight into the underlying physics of vortex-‐induced separation & buffeting and role of aero-‐elastic coupling
Multiple modes of interaction identified: dipole formation, loss of vortex coherence & vortex bifurcation
Incident vortex
Static aeroelastic deflection modifies interaction thru repositioning of incident vortex
Rigid wing Flexible wing
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. 88ABW-2014-3059
Flow/Acoustic Interactions on SUAS
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ü Close-‐range ISR dictates the introduction of SUAS’s ü Need to remain undetected for low-‐altitude operation in presence of moderate gusts ü Vehicle size/speed result in transitional flows which may give rise to tonal-‐noise emission
compromising location due to aural detection ü Difficult to do experimentally due to wind tunnel environment
OBJECTIVES: ü Improve understanding/prediction of noise generation in transitional/turbulent flows
ü Study role of laminar separation and transition (T-‐S waves) on resonance and tonal noise generation
ü Study impact of disturbances (gusts, maneuvering, deUlections) on sound radiation
ü Reveal approaches for noise abatement ü Guide design-‐oriented approaches
Canonical conOigurations High-‐Oidelity overset simulations
Leverage OSU acous3c analysis tool development
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. 88ABW-2014-3059
Example of Sound Radiation During Onset of Unsteady Separation Over Pitching Airfoil
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x/c = 0.01
LE separation
transition
x/c = 0.2
DSV
α = 18.6o
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. 88ABW-2014-3059
Plasma-Based Control of Transitional Flows
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ü Plasma-‐based flow control techniques offers potential for manipulation of transitional/turbulent flows in future vehicles
ü BeneOits include: delay/induce transition, drag and noise reduction ü Strategies for effective control need to be explored ü Active flow control requires high-‐fidelity physics-‐based approaches
Objectives ü Explore flow control strategies for canonical conUigurations including control of transition on upswept and swept wing sections using several plasma-‐based approaches
üImproved strategies for transition manipulation in drag and noise reduction applications üControl of dangerous Ulexible vehicle response due to large excursions in transition location
Plasma-‐based control devices & canonical conOigurations
Leverage OSU experimental/comp plasma flow control research
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. 88ABW-2014-3059
Control of Transition Induced by Surface Imperfections
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ü Surface excrescences such as bumps, mismatched panels, gaps and other imperfection or contamination can generate premature transition to turbulent flow over a wing surface
ü Critical to system performance (i.e., range, payload, loiter time, fuel consumption)
ü Difficult to do experimentally
Objectives ü Perform high-‐Uidelity Uirst-‐principles simulation of canonical conUigurations for T-‐S and crossflow instability ü Characterize effects of pressure gradient, incoming disturbances ü Compare to standard lower-‐Uidelity approaches (N-‐factor, PSE) ü Help establish manufacturing or surface damage tolerances
canonical conOigurations
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. 88ABW-2014-3059
Aero-Optical Aberration in Supersonic Flows
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ü Laser integration is being considered for FAD concepts ü Required for targeting, lasercomm, self-‐protection, soft ground targets, etc.. ü Limited knowledge is available on aero-‐optical aberration in supersonic flows ü This brings uncertainty to current HEL-‐FAD trade space studies
OBJECTIVES: ü Characterize aero-‐optical aberration in canonical transonic/supersonic flows relevant to HEL-‐FAD integration
ü Characterize aberration effects of post-‐shock boundary layer and shock motion (jitter)
üProvide guidance to HEL-‐FAD trade space studies üEstablish computational requirements for reliable aero-‐optic prediction üSuggest strategies for aberration mitigation
canonical conOigurations Previous emphasis: ATL-‐type turrets & shear layers
Standard grid Aero-‐optics grid
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. 88ABW-2014-3059
Response of Flexible Panels in Supersonic Flow
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ü Supersonic low over elastic surfaces may give rise to complex interactions leading to limit-‐cycle oscillations, fatigue and acoustic radiation
ü Important to supersonic aircraft and hot descent of hypersonic vehicles
ü Complex coupling of deformations with transition and separation due to shock impingement
ü Impacts vehicle performance due to weight considerations
canonical conOigurations
Shock impingement
Coupling of transition with surface vibrations
Flow parameters Mach No.,
p3 / p1 (or σ ) Re , δ / a, pc , xi /a
Large number of Uluid/structural parameters
Objectives: ü Explore complex dynamics of flexible panels in low supersonic flow (M< 2) using LES and simple structural models
ü Explore effects of shock impingement, non-‐isotropic structure üDiscover new aero-‐elastic instability regimes and potential role of flexibility as passive flow control mechanism üIdentify dangerous panel interactions
Structural parameters λ = ρ2 U3 a /D h / a , µs = 0.1 ; a / b = 0
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. 88ABW-2014-3059
Oblique Shock Impingement on a Flexible Panel: Inviscid Interaction
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supercritical bifurcation
subcritical bifurcation
M1 = 2, p3/p1 = 1.4, λ = 875
supercritical bifurcation
M1 = 2
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. 88ABW-2014-3059
Laminar Interactions over a Flexible Panel in Supersonic Flow
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oscillations correlate with stability analysis and is suppressed for a cooled wall
Coupling of instability waves with flexible panel modes
M = 2.0, Rea = 300,000, δ /a = 0.015, λ = 500
Comparison with linear stability analysis rigid flexible
Coupling of panel flexural waves with shear layer modes provides “passive” control of separation
rigid flexible
Laminar SBLI over Ulexible panel p3 / p1 = 1.8, Rea = 120,000, λ = 875
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. 88ABW-2014-3059
DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. 88ABW-2014-3059